Circular knitting machine with knitting function

ABSTRACT

A circular knitting machine includes a needle cylinder rotating around a vertical axis and a sinker ring rotating with the needle cylinder. The needle cylinder has in its outer edge portion vertically controllable tip needles with needle hooks opened downwards as loop-forming elements, and for each tip needle, a surrounding sinker supporting the loop-formation is held movable in the radial direction on the sinker ring. Further, for each tip needle on the needle cylinder, a press sinker is kept on the sinker ring horizontally in radial direction, to close the hook tip of the tip needle by pressing the needle tip to the needle shaft. The press sinkers are each disposed on the sinker ring between two adjacent surrounding sinkers. The circular knitting machine allows needle wear to be reduced and a selection between weft knitting and warp knitting as loop-forming techniques is enabled in a single machine.

The present invention relates to a circular knitting machine with less wear of machine parts, in particular of loop-forming elements, as well as a wider range of possible loop-forming techniques.

Conventional circular knitting machines use tongue needles as central loop-forming elements. These are guided on a rotating needle cylinder and expelled and retracted (moved upwards or downwards) according to their guidance in the locking parts.

When loops are formed on a knitting system of such a circular knitting machine, the tongue of a passing and upwardly expelled tongue needle is first opened by a loop on the needle shaft relative to this downward sliding previously formed loop and then closed again during the looping (Kulieren) and the retraction of the needle from the loop sliding upwards along the needle shaft relative to the needle shaft. The opening and closing processes of the tongue needle take place via a tongue hinge. Due to the frequency of their continuous actuation, possibly with the influence of considerable yarn tensions, the tongue hinges of the tongue needles and with them the tongue needles are naturally particularly prone to wear inside a knitting machine.

The failure of a tongue hinge leads to incorrect loop formation and thus to errors in the knitting ware. The replacement of the affected tongue needle requires the knitting machine to stop. Due to the large number of tongue needles in the needle cylinder, such failures can affect the operation of the knitting machine to a considerable extent. However, the problems are not only the resulting interruptions in operation, but also the relatively high costs for tongue needles, the production of which is expensive due to the required mechanical load capacity.

Therefore, the use of simpler and less damageable needle types in knitting machines is of particular interest. A needle type with a simpler structure, especially without a mechanically movable joint, is the tip needle, whose hook is open at the top of the needle downwards. The needle hook can be closed elastically by external pressure towards the needle shaft.

Such circular knitting machines working with tip needles are described in the document DE 1 635 878 A and DE 361 135.

When knitting in a circular knitting machine with tip needles, the needle hook must be elastically closed from the outside by means of a pressing wheel when the needle is pulled off (during the looping), so that it does not pick up the old loop in addition to the new yarn. Such a pressing wheel is provided outside the needle cylinder and, in order to minimize frictional forces between the passing needle hooks and the pressing wheel, is preferably provided actively or passively co-rotating. Due to the different diameters of the large needle cylinder and the significantly smaller pressing wheel, however, tangential forces acting on the needle cannot be completely avoided. Since such a pressing wheel has to be provided for each knitting system, there is also a considerable space requirement for the pressing wheels, which particularly restricts the possible system density, i.e. the number of knitting systems per inch of the needle cylinder circumference.

Alternatively, each tip needle of such a circular knitting machine can be provided with a needle press running parallel to the needle shaft, which presses on the needle hook during the looping (Kulieren) from the outside and closes it. However, the presence of a large number of pairs of tip needles and needle presses on the needle cylinder may again cause problems with wear susceptibility.

The present invention is therefore based on the problem of creating a circular knitting machine working with tip needles instead of tongue needles, which with the simplest possible construction has a lower susceptibility to wear, in particular with respect to the needles, than the conventional circular knitting machine with tongue needles.

This object is solved by the circular knitting machine of the present invention as defined in claim 1. Further advantageous embodiments can be found in the dependent claims.

The circular knitting machine according to the invention has a needle cylinder rotating around a vertical axis and a sinker ring rotating with the needle cylinder. The needle cylinder is provided in its outer edge portion with vertically controllable, in particular upwards expellable, tip needles having needle hooks opened downwards as loop-forming elements, and for each tip needle, a surrounding sinker, which supports the loop-formation, is held to be displaceable horizontally in radial direction on the needle cylinder. Further, for each tip needle on the needle cylinder, a press sinker on the sinker ring is held to be displaceable horizontally in radial direction, to close the hook tip of the tip needle by pressing the needle tip to the needle shaft. The press sinkers are each arranged on the sinker ring between two adjacent surrounding sinkers, as space-saving as possible and with little or as low clearance as possible.

In the circular knitting machine according to the invention, the loops are formed by the coordinated vertical or horizontal movements of the needles and the corresponding surrounding sinkers for pushing the yarn to the needle shafts. Each surrounding sinker has two horizontal planes in its profile facing the corresponding needle with an intermediate nose projecting towards the needle. The lower of the two support planes serves as a plane on which the knitted ware rests, while the upper support plane guides the new yarn towards the needle shaft and attaches it thereto. The vertical distance between the two planes serves to separate the loop head of the old loop on the sinker plane from the new yarn in the height, thus creating a safety distance over which the needle hook can be closed when the needle is pulled vertically, so that only the new yarn enters the needle hook.

Furthermore, the circular knitting machine according to the invention comprises a further sinker for each needle, namely the press sinker. The press sinker is used to press on the needle hook when the needle is pulled off and to tighten it elastically. The press sinkers rotate with the needles and the surrounding sinkers, so that no tangential forces occur between the press sinker and the needle hook when pressing the needle hook.

The press sinkers are guided together with the surrounding sinkers on the sinker ring co-rotating with the needle cylinder. The alternating adjacent surrounding sinkers and press sinkers are as close as possible to each other, i.e. with the lowest possible clearance. If separation bars are provided between the surrounding sinkers to improve their guidance during expelling and retracting, the press sinkers can also be mounted on these separation bars. The expelling and retraction of the surrounding sinkers on the one hand and the press sinkers on the other are controlled independently of each other.

The outer structure of the circular knitting machine according to the invention differs from that of conventional circular knitting machines on the one hand by the use of tip needles instead of tongue needles and on the other hand by the additional insertion of press sinkers into the spaces between the surrounding sinkers. The additional space requirement is therefore comparatively small, in particular because of the tight arrangement of the press sinkers between the surrounding sinkers, for example on their separating bars. The press sinkers are arranged largely without lateral clearance between two adjacent surrounding sinkers and, due to their co-rotation with the needles, exert no tangential forces on them during their radial ejection against the needle tip. This thus counteracts excessive wear on the needles and on the surrounding sinkers and press sinkers of the circular knitting machine according to the invention.

A further advantage of the circular knitting machine according to the invention is its usability for the production of knitted fabrics both according to the weft knitting principle and according to the warp knitting principle. In fact, the circular knitting machine can be switched to both loop-forming techniques or at least pre-set. When the needle is in the ejected state, depending on whether the new yarn is guided from the surrounding sinker only to the needle shaft, or whether the surrounding sinker is expelled to a position beyond the radial needle position and thereby presents a loop with the yarn, the loops formed by the machine are generated according to the weft knitting or warp knitting principle. While the yarn is held under tension at the needle shaft before looping in case of weft knitting, in the case of warp knitting, yarn loops are provided under lower tension. Also during the looping process (“Kulieren”), the yarn tension is lower than in weft knitting.

The circular knitting machine according to the invention can therefore be equipped with a control device for controlling the positioning of the individual surrounding sinkers, the individual press sinkers or both sinker types. In this way, the radial displacements of surrounding sinkers can be controlled in such a way that they guide the new yarn to the needle shaft before retracting the respective tip needles, so that the respective loop-forming systems are knitted. The surrounding sinkers can also be controlled so that they guide the new yarn past the needle shaft in the radial direction and thereby provide a loop so that (warp) knitting is carried out at the loop-forming systems.

The circular knitting machine can be operated as a warp knitting machine by appropriate control of the yarn tension on the one hand and the radial retraction movement of its surrounding sinkers on the other hand (with appropriately fixed adjustment of the locking parts of the surrounding sinkers the machine according to the invention can also be operated as a circular warp knitting machine). The optional switching between weft knitting and warp knitting can be done, for example, by means of adjustable sliders, which move the surrounding sinkers in the radial direction, respectively. By appropriate adjustment of the sliders and thus the positioning of the surrounding sinkers in the radial direction, the circular knitting machine according to the invention can also simultaneously generate loops according to weft the knitting process and the warp knitting process on its various systems.

The loop-forming systems of the circular knitting machine according to the invention can be pre-adjusted or controlled or switched during operation so that the respective tip needles form loops from the respective supplied yarn loops according to the weft knitting principle or the warp knitting principle, catch the supplied yarn or remain in circular motion.

During the catching process, the tips of the corresponding loop-forming system are retracted at an earlier time than in the weft knitting or warp knitting process, so that the press sinkers close the hooks of the respective tip needles only when both the supplied yarn and a previous loop have been received within the hook. Alternatively, the catching process can be carried out by moving the press sinkers not so close to the hook of the respective needle as to close it so that both the supplied yarn and the old loop inside the hook can be received.

It turns out that the use of tip needles in the circular knitting machine according to the invention has further advantages. For example, the needle head of a tip needle is generally smaller than that of a tongue needle, so that an undesirable widening of the loops by the needle head is a smaller problem. At the same fineness, smaller loops are possible. Further, the loops cannot be damaged by the opening and closing needle tongues and their hinges. Due to the lower strain on the yarn, undesirable effects such as flattening, excessive pilling tendency, unequal heights of handles in plush or lining as well as twisting of the yarns during plating (by the smaller needle head) are largely avoided.

The use of tip needles also allows an increase of the rotating speed of the needle cylinder, since there is no need to ensure the absorption of the kinetic rotational energy of the needle tongues.

The use of elastically lockable tip needles instead of the tongue needles that can be closed via their tongue hinge also reduces the knitting energy and thus the overall power consumption of the circular knitting machine.

Cost advantages are mainly due to the lower price of tip needles compared to tongue needles; but also the longer needle life of peak needles due to their simpler, less frail construction is another advantageous cost factor. It is also advantageous that the start of the knitting process is simplified after an interruption of the operation when tip needles are used instead of tongue needles; the latter must be checked before start of the knitting to see whether their tongues are in the correct opening or closing state.

In the following, an embodiment as well as further advantages and details of the present invention are described with reference to the attached drawings.

The FIGS. 1a to 1h (with enlarged representation in FIG. 1a ) show the sequence of the loop-forming method according to the (weft) knitting principle in the circular knitting machine according to the invention.

FIGS. 2a and 2b each show the different positions of the loop-forming elements before pulling off the needle during warp knitting and weft knitting with the circular knitting machine according to the invention.

FIG. 3a shows the position of the loop elements during pulling off/retracting of the needle during the catching process, while FIG. 3b shows the needle movement curve during the catching process.

FIG. 4a shows a perspective close-up view of the edge portion of the needle cylinder with needles as well as corresponding surrounding sinkers and press sinkers and the corresponding sinker locks (in contrast to the circular knitting of FIGS. 2a and 2b , the sinker lock and sinker lock part are integrated in this case). FIG. 4b shows a detailed view of the weft knitting or warp knitting system in FIG. 4 a.

FIG. 5 shows a cross-sectional view of the sinker ring and the surrounding sinkers and press sinkers supported thereon in a parallel section direction which is parallel to the tangential direction on the needle cylinder.

FIG. 6 shows a variant of a two-piece tip needle that can be used in the circular knitting machine, in two views, one with the two needle parts separated from each other and one in the composite state.

In FIGS. 1a to 1h , the loop formation according to the (weft) knitting principle is shown on a loop-forming system of the circular knitting machine according to the invention. FIG. 1a shows in enlarged representation the tip needle 2 in the needle cylinder. By appropriate guidance of its control foot 6 in a cylinder lock part 14, the needle is expelled in the vertical direction and removed. In FIG. 1a the needle is in the pulled-off state. In its hook tip, there is the previously formed “old” loop of the already produced knitted fabric. The needle 2 is now expelled upwards, while the old loop remains on the plane (the lower support plane) 3 a of the surrounding sinker 3 and is held back by the nose 3 c of the sinker profile. As soon as the needle 2 has reached its highest position, the surrounding sinker 3 stored on the sinker ring 19 is ejected outwards (to the right in the drawing) guided by the control foot 8 in the sinker lock part 10, see FIG. 1 b.

In FIG. 1c , the needle 2 now passes the yarn guide 5 on its rotation path. Then, the surrounding sinker 3 in FIG. 1d is extended in the radial direction inwards (to the left in the drawing) in the direction of the needle and the new yarn 1 is pushed to the shaft from the is extended 3 above the upper support plane 3 b in the direction of the shaft of the expelled needle 2.

The needle 2 is then pulled down/retracted in FIG. 1e , so that the yarn lying on the upper support plane 3 b of the surrounding sinker 3 is received in the needle hook. Then, in FIG. 1f , the press sinker 4 is extended by appropriate guidance of its control foot 7 inwards in the direction of the needle, so that it closes the needle hook elastically by pressure from the outside. Now in FIG. 1g the surrounding sinker 3 is pulled back so far that its upper support plane 3 b releases the new yarn 1, while the needle 2 is simultaneously pulled further downwards, so that the needle hook and with it the yarn 1 therein are pulled through the through the old loop which is still on the plane 3 a. Subsequently, in FIG. 1h , the press sinker 4 is retracted and the pull-off process of the needle 2 is completed (loop-formation, “Kulierung”), whereby the looping process is completed and can start again in the position of FIG. 1 a.

FIGS. 2a and 2b show two snapshots of a weft knitting or warp knitting process in the circular knitting machine according to the invention. FIG. 2b shows the position of the loop forming elements in the knitting process immediately before pulling off the needle 2 and thus corresponds approximately to the position in FIG. 1d (the needles and sinkers of the machine in FIGS. 2a and 2b differ slightly from those in FIGS. 1a to 1h ). In FIG. 2a , the corresponding snapshot is depicted in the warp knitting process. The surrounding sinker 3 is extended further inwards (to the left in the drawing) in comparison to the weft knitting process and thus presents a yarn loop reaching from the needle shaft to the upper support plane 3 b. While the yarn is kept under uniform tension as continuously as possible by appropriate means (such as a suitable feeder) in the knitting process in FIG. 2b with a view to a good quality of the produced knitted fabric, the yarn tension can be lower in the warp knitting process in FIG. 2a and can vary. The provision of the yarn loop by the further advancing of the surrounding sinker ensures a safe loop-forming process.

Both in the situation of the warp knitting process in FIG. 2a as well as in the weft knitting process in FIG. 2b , in the next steps, the needle hooks are closed by the press sinker 4, the needle 2 is removed and the new yarn 1 on the needle shaft or the provided yarn loop are thus received to be then pulled through the old loop.

The circular knitting machine according to the invention is therefore suitable both for weft knitting and for warp knitting. In fact, the machine may have an actuator 15 on the sinker lock 9, with which a sinker lock part 10 can be displaced, whereby the length of the ejection path of the surrounding sinker 3 is switched between a longer path for warp knitting and a shorter path for weft knitting. The sinker lock 9 screwed to the sinker lock support ring 12.

Due the option of switching between the weft knitting function and warp knitting function, the circular knitting machine according to the invention allows an efficient and safe processing of a variety of different yarns. In particular, the warp knitting function allows the use of more sensitive yarns due to the lower yarn tension in the process. In fact, the loop-formation in the warp knitting process according to FIG. 2a takes place in the two steps of providing a yarn loop and pulling the provided yarn loop through the old loop. In the first step, the yarn tension in the yarn loop first increases from friction point to friction point due to the rope friction principle and then, when the yarn loop is presented, drops back to zero. In the second step, when the yarn loop is pulled through the old loop, yarn sections of the yarn loop and of the old loop rub against each other, thereby increasing the yarn tension again.

In contrast, in weft knitting, the conveying of the new yarn through the yarn guide and the pulling of the yarn through the old loop are simultaneously carried out, whereby the corresponding yarn friction forces add up and together result in a significantly higher yarn tension. Such an addition of yarn forces does not take place in warp knitting due to the temporal offset of the two processing steps, whereby the maximum occurring yarn tensions are lower. The warp knitting process is thus more preserving for both the yarn to be processed and for the loop-forming elements of the circular knitting machine.

The presentation of the yarn loop in the warp knitting process also has the advantage that the loop-forming part in the cylinder lock is relieved. The loop-forming angles therein are less steep than for weft knitting, which in turn reduces the load on the needle guided in the loop-forming part. By using simpler loop-forming parts, needle foot fractures and needle head fractures can be avoided.

In order to allow patterns, the weft knitting or warp knitting systems of a circular knitting machine that can be used for weft knitting and warp knitting should also be able to be adjusted for circular running and catching.

During the circular running, the needle 2 simply remains in its circular running position by appropriate control of the lock parts and is not expelled at all. The new yarn 1 is not even received by the needle hook.

FIG. 3a shows the position of the knitting system in the catching process, more precisely during the retraction of the needle 2. After the needle 2 has just before been ejected so far that it has received the new yarn 1, both the new yarn 1 and the old loop remain in the needle hook when retracted.

The catching process can be controlled by appropriate control of either the needle retraction or of the displacement of the press sinker 4. Thus, an earlier retraction of the needle 2 can be adjusted so that the press sinker 4 closes the needle hook only when the opening of the needle hook has already passed the old loop lying on the plane 3 a (which is therefore already inside the needle hook).

FIG. 3b shows the needle movement curves for the weft knitting process and the catching process side by side. While the solid line 16 represents the needle movement along the timeline during the weft knitting process, the interrupted line 17 shows the earlier retraction of the tip needle 2 during the catching process.

Another possibility to implement the catching process with the circular knitting machine according to the invention is to not at all extend the press sinker 4 on a selected knitting system to close the hook needle, but to maintain it in its retracted position without pressure contact to the needle hook. The corresponding control of the press sinker 4 is done, for example, by a suitable adjustment of the sinker locks on the respective systems.

FIG. 4a shows a perspective view of the needle cylinder 11 from the side (in the variant shown here, the sinker lock 9 and the sinker lock part 10 are integrated). In FIG. 4b , the section showing the knitting system with yarn guide 5 is shown in detail. In both figures, the tip needles 2, which are arranged in the entire circumferential range of the needle cylinder 11, are shown only in a partial portion of the cylinder circumference for clarity. The figures, in particular FIG. 4b , show in addition to the needles 2 and the surrounding sinkers 3 and press sinkers 4 also the yarn guide 5 belonging to the knitting site in the selected portion of the cylinder edge. The surrounding sinkers 3 extend from the sinker ring 19 from the outside to the inside between the needles 2 on the sinker guides arranged on the needle cylinder. The press sinkers 4 are each arranged between two adjacent surrounding sinkers 3 essentially without any clearance (see also FIG. 5) and thus directly face the corresponding tip needle. The tip needles are also arranged between the surrounding sinkers extending towards the sinker guides to the board guides, so that the surrounding sinkers serve as guides for both the press sinkers and the needles.

As shown in FIG. 5, the press sinkers 4 thereby require little additional space because even with a conventional circular knitting machine, in which tongue needles but no press sinker are used, the surrounding sinkers 3 are spaced from each other (so that they can be guided past by the needles when they are expelled). In such a conventional knitting machine, separating bars 18 are normally provided on the sinker ring 19 in the spaces between the surrounding sinkers 3 to avoid clearance between the surrounding sinkers 3. Such a machine can be modified to a circular knitting machine according to the invention by arranging the press sinkers 4 on the separating bars 18, reasonably with as little clearance as possible with respect to the adjacent surrounding sinkers 3. Alternatively, a respective surrounding sinker and press sinker could also share a channel delimited by corresponding separating bars. However, this would have the disadvantage that the separating bars should be as thin as possible in view of a high fineness, which would entail an increased risk of breakage of the separating bars.

Just like the tip needles 2 having needle feet 6, which run through appropriately pre-set lock channels during rotation, the surrounding sinkers 3 and press sinker 4 also each have sinker feet 7 and 8 which are guided in corresponding channels of the sinker lock part 10. By appropriate presetting of the needle locks and sinker locks, each knitting system can optionally be adjusted so that loops are formed either according to the weft knitting principle or according to the warp knitting principle, catches the new yarn only or remains in a circular running state. In FIGS. 4a and 4b , the switch between weft knitting and warp knitting function is carried out by the actuator 15 on the sinker lock with integrated sinker lock part.

The space-saving arrangement of the press sinkers 4 between the surrounding sinkers 3 allows a relatively high fineness of the circular knitting machine, i.e. a large number of needles per inch at the cylinder circumference. Another advantage of this space-saving arrangement is that a high number of knitting systems can also be arranged along the circumference of the needle cylinder. Thus, with a circular knitting machine having a needle cylinder circumference of 30 inches, more than 88 knitting systems can be provided, which corresponds to a high system density of 2.9 systems per inch (higher system densities up to 3.2 are also conceivable).

FIG. 6 illustrates another possible simplification, which is the use of two-piece tip needles in the circular knitting machine. Such a two-piece tip needle has an upper tip needle part 2′ and a lower control foot part 6′. The tip needle part 2′ extends from the needle hook at the upper end along the needle shaft to a nose protruding to the side, while the control foot part 6′ has a gap-like recess receiving the nose and has the contour profile required for receiving and guiding in the corresponding cylinder lock part. The needle part 2′ can then preferably be formed by simple forming a wire, which is bent at the upper end towards the needle hook and towards the nose at the lower end, while another method such as punching a sheet metal part can be used for the control foot part 6′. The nose of the needle part 2′ and the recess of the control foot part 6′ are engaged with each other, but are not limited in their form apart from this adapter function; in particular, the recess in the control foot part does not need to have a slotted or slit shape.

The use of two-piece tip needles can also bring about further cost advantages, if only the more cost-effective needle parts 2′ of the tip needles have to be replaced after wear. Depending on the selection of the manufacturing processes for the needle parts, a complete needle equipment of the circular knitting machine can be more cost-effective. This partition of the needle in two parts, optionally in combination with the optional insertion of the press sinkers 3 between the surrounding sinkers 4, also allows an even easier conversion of a circular knitting machine with wrap knitting function into a conventional circular knitting machine and vice versa.

Alternatively, the present invention can also be applied to circular knitting machines based on the principle of the so-called relative technology. In such machines, the surrounding sinkers are stored in the upper part of the needle cylinder between the needles. Therefore, this machine type does not require a separate sinker ring. The surrounding sinkers can be controlled vertically in height and at the same time perform a pivoting motion around their pivot point. This pivoting motion replaces the horizontal movement of a conventional surrounding sinker. As pressing elements for closing the needle hooks, pressing wheels arranged outside the needle cylinder circumference can be used here (one for each loop-forming system, respectively).

The structure of the circular knitting machine according to the invention is based on a further development of conventional circular knitting machines. The circular knitting machine according to the invention can be manufactured as an independent machine; however, it is also conceivable, for example, to expand a conventional circular knitting machine by simply adding press sinkers into the already existing gaps between the surrounding sinkers as well as by the replacement of tongue needles by tip needles or the replacement of needle parts of corresponding two-piece tongue needles and tip needles.

In any case, the invention provides considerable advantages with regard to the problem of needle wear. In addition, the machine according to the invention allows the choice between weft knitting and warp knitting as the loop-forming techniques within a single machine.

REFERENCE SIGN LIST

-   1 yarn -   2 needle -   2′ needle part -   3 surrounding sinker -   3 a lower support plane -   3 b upper support plane -   3 c nose of the surrounding sinker profile -   4 press sinker -   5 yarn guide -   6 Control foot of the needle -   6′ control foot part -   7 Control foot of the press sinker -   8 Control foot of the surrounding sinker -   9 sinker lock -   10 sinker lock part -   11 needle cylinder -   12 sinker lock support ring -   13 cylinder lock -   14 cylinder lock part -   15 actuator for weft knitting/warp knitting -   16 knitting curve -   17 catching curve -   18 separation bar -   19 sinker ring 

1-14. (canceled)
 15. A circular knitting machine, comprising: a needle cylinder rotating around a vertical axis; and a sinker ring rotating with said needle cylinder; said needle cylinder having an outer edge portion and vertically controllable tip needles in said outer edge portion, said tip needles having needle hooks opened downwards as loop-forming elements and needle shafts; a surrounding sinker supporting loop-formation being held movably in a radial direction on said sinker ring for each respective tip needle on said needle cylinder; a press sinker held movably in the radial direction on said sinker ring for each respective tip needle on said needle cylinder to allow a closing of said needle hooks of said tip needle by pressing to said needle shaft; and said press sinkers each being disposed between two adjacent surrounding sinkers.
 16. The circular knitting machine according to claim 15, wherein said press sinkers on said sinker ring are disposed between said adjacent surrounding sinkers on both sides substantially without clearance.
 17. The circular knitting machine according to claim 15, which further comprises separating bars extended between said adjacent surrounding sinkers, said press sinkers each being guided on said sinker ring on said separating bars.
 18. The circular knitting machine according to claim 15, wherein said surrounding sinkers have a side profile facing said needle and two horizontal support planes in side profile with an intermediate nose protruding in the radial direction.
 19. The circular knitting machine according to claim 15, which further comprises a control device for individually controlling a radial displacement of at least one of said surrounding sinkers or said press sinkers.
 20. The circular knitting machine according to claim 19, wherein said control device is configured to control said radial displacement of one or more of said surrounding sinkers or of all of said surrounding sinkers for guiding a new yarn toward said needle shaft before a retraction of respective tip needles to permit said tip needle to form loops of a weft knitted fabric.
 21. The circular knitting machine according to claim 19, wherein said control device is configured to control said radial displacement of one or more surrounding sinkers or of all surrounding sinkers for guiding a new yarn past said needle shaft before a retraction of respective tip needles in a radial direction and thus for providing a yarn loop to permit said tip needle to form loops of a warp knitted fabric.
 22. The circular knitting machine according to claim 15, which further comprises: a plurality of yarn feeders; said tip needles cooperating in a joint loop formation for a supplied yarn and each forming a loop-forming system; and each loop-forming system being adjustable in advance causing said tip needles to form loops either according to a weft knitting principle or a warp knitting principle.
 23. The circular knitting machine according to claim 22, which further comprises: a sinker lock for guiding control feet of said surrounding sinkers and said press sinkers; said sinker lock configured to be changed for forming loops at said loop-forming systems either according to the weft knitting principle or the warp knitting principle.
 24. The circular knitting machine according to claim 15, which further comprises: a plurality of yarn feeders; said tip needles cooperating in a joint loop-formation for a supplied yarn and each forming a loop-forming system; and each loop-forming system being adjustable in advance causing said tip needles to form loops, catch a supplied yarn or remain in a circular run.
 25. The circular knitting machine according to claim 22, which further comprises a control device for controlling each loop-forming system to cause said tip needles to form the loops according to the weft knitting principle or the warp knitting principle or catch a supplied yarn or remain in a circular run.
 26. The circular knitting machine according to claim 22, wherein said tip needles of a loop-forming system carrying out a catching process are retracted earlier than in the loop forming process, causing said press sinkers to close said hooks of respective tip needles only when both a supplied yarn and a previous loop have been received within said hook.
 27. The circular knitting machine according to claim 22, wherein said press sinkers belonging to said tip needles of a loop-forming system performing a catching process are not moved so close to said hook of a respective needle that they close said hook, so that both a supplied yarn and a previous loop are received within said hook.
 28. The circular knitting machine according to claim 15, wherein said tip needle includes an upper needle part with a nose protruding to a side and a lower control foot part with a recess for receiving said nose of said needle part. 